CN102365784B - Reflectionless filters - Google Patents

Abstract

Reflectionless low-pass, high-pass, band-pass, and band-stop filters, as well as a method for designing such filters is disclosed, The niters function by absorbing the slop- band portion of the spectrum rather than reflecting it back to the source, which has significant advantages in many different applications.

Description

Reflectionless filter

The reference of related application

The application requires the U.S. Provisional Application No.61/150 that is entitled as " reflectionless filter " submitting on February 9th, 2009,868 priority number, and its full content is clearly hereby expressly incorporated by reference thus.

Background technology

1. technical field

The present invention relates to electronic filter and using method thereof.Particularly, the present invention relates to areflexia electronic filter and using method thereof.

2. background technology

Filter is ubiquitous assembly in the nearly all electronic system from communication to radio astronomy, and since more than halfth century, has thought that the basic principle of filter theory and optimization is well-known.But the design and implementation of practical filter remains one of most active research field of current electronics circle.But the stopband part that makes frequency spectrum is absorbed but not is reflected back to the reflectionless filter in source, out in the cold to a great extent.

Standard reflection filter can cause many problems in many application, comprising: (1) sensitiveness with external port terminal frequency mixer performance; (2) there is the high-band latent instability of the integrated amplifier of gain outward; (3) the harmful or unpredictable nonlinear effect that idle harmonic load causes; (4) potential damage of the high power transmission device that harmonic content is large; (5) at filter be coupled to catching leakage that energy causes, disturb or crosstalk between another indoor not good matching component of enclosed cavity.

Have many actual conditions, the reactive termination being presented in its stopband by conventional filter among this affects systematic function.For example, frequency mixer is extremely responsive for being present in the outer terminal of band on its any port, and this filter most possible situation in many heterodynes application just.Broadband system designer solves this problem by inserting fixed attenuator near signal path frequency mixer conventionally.Same, high-gain amplifier (although they may in test fixing device absolute stability) can easily form the unsteadiness in enclosed environment, and in this enclosed environment, unexpected feedback combines with terminal outside idle band on it inputs or outputs.Equally, filter conventionally contiguous amplifier uses, and to determine better system bandwidth, and the rejector impedance of filter may need to install additional attenuator, to avoid causing stability problem.

A conventional way of the filter that preparation matches with passband and stopband simultaneously, that one of design is used two or more to have the duplexer (or multiplexer) from the complementary mechanical admittance curves filter of independent loading (reflection) prototype, and all filters of termination except these filters and filter load matched.This is a quite complicated process, need to make at least to double as the quantity of the different assemblies of phase same order conventional filter, and can only on of a two ports port, mate.Another kind of optional design is by two quadrature hybrid or by preparing directional filter with directional coupled structure in equilibrium allocation.But, be difficult to design the quadrature hybrid with enough bandwidth, and directional filter structure is not suitable for self to carry out for high-order in fact.

Therefore, wish to have the reflectionless filter of signal reflex not being got back to source in its stopband.In addition, wish to have under all frequencies and at two reflectionless filters that port match is good.

Summary of the invention

The present invention is devoted to solve some problem and the shortcomings relevant to conventional filter, and the new resources that are suitable for band selection and are suitable for defining in electronic system are provided.

Inventive embodiment relates to reflectionless filter.This filter can be symmetrical two-port circuit, and it comprises that at least one can't harm element substantially and at least one damages element substantially.Symmetric circuit can be divided into two parts along line of symmetry, and when port is during respectively with homophase and 180 ° of driven out-of-phase, utilizes even-mode and odd mode equivalent electric circuit, can form symmetric circuit.In addition,, for selected normalized impedance, the standardization input impedance of even-mode equivalent electric circuit can equal the standardization input admittance of odd mode equivalent electric circuit substantially.

Filter can have at least one harmless element, and what it can be that inductor, capacitor, variable capacitance diode, resonator and transmission line and/or at least one can be resistor damages the wherein a kind of of element.In certain embodiments, at least one circuit element is tunable.

Filter can be low pass filter, high pass filter, band pass filter or a band stop filter.Filter also can be included at least one vent diverter between circuit node and line of symmetry.Filter can be single order, second order or higher order filter.

In certain embodiments, all inductors all have identical value, and all capacitors have identical value.In addition all resistors can have identical value.

In certain embodiments, filter can be one of band pass filter and band stop filter, and all resistors can have identical value, and all inductors are one of two values, and all capacitors are one of two values.

In certain embodiments, filter is one of low pass filter and high pass filter, and

$L=\frac{Z_0}{{\mathrm{\ω}}_p}$

$C=\frac{Y_0}{{\mathrm{\ω}}_p}$

R＝Z ₀

Wherein L is the inductance of all inductors, and C is the electric capacity of all capacitors, and R is the resistance of all resistance, ω _pthe pole frequency of radian per second, Y ₀for normalized admittance, and Z ₀it is normalized impedance.

In other embodiments, filter is one of band pass filter and band stop filter, has the first limit and the second limit, and

$L_s=\frac{Z_0}{{\mathrm{\ω}}_s}$

$L_x=\frac{Z_0}{{\mathrm{\ω}}_x}$

$C_s=\frac{Y_0}{{\mathrm{\ω}}_s}$

$C_x=\frac{Y_0}{{\mathrm{\ω}}_x}$

R＝Z ₀

Wherein the inductance of inductor is L _xand L _sone of, the electric capacity of capacitor is C _xand C _sone of, the resistance of resistor is R, Y ₀for normalized admittance, Z ₀normalized impedance, and

ω _s＝ω _p，2-ω _p，1

${\mathrm{\ω}}_x=\frac{{\mathrm{\ω}}_{p,1}{\mathrm{\ω}}_{p,2}}{{\mathrm{\ω}}_{p,2}-{\mathrm{\ω}}_{p,1}}$

Wherein ω _{p, 1}and ω _{p, 2}respectively the first and second pole frequencies.

In certain embodiments, two symmetrical can comprising half circuit a: port node, the first internal node, the second internal node, port node is connected to the harmless element of the first type of node on line of symmetry, port node is connected to the harmless element of the second type of the first internal node, by the harmless element of the first type of the first internal node ground connection, the first internal node is connected to the element that damages of the second internal node, by the harmless element of the second type of the second internal node ground connection, and the direct connection between node on the second internal node and line of symmetry.

Damaging element can be a resistor.The harmless element of the first type can be an inductor, and the harmless element of the second type can be a capacitor or vice versa.In other embodiments, the harmless element of the first type is inductor and capacitor in parallel, and the harmless element of the second type is inductor and the capacitor of series connection.But in other embodiments, the harmless element of the first type is inductor and the capacitor of series connection, and the harmless element of the second type is inductor and capacitor in parallel.

In certain embodiments, many reflectionless filters can cascade.The limit of cascading filter can overlap or disperse.Filter can be obtained by the convergent-divergent of another reflectionless filter or conversion.Circuit element can be equivalence or the approximate transmission line of lamped element, and/or equivalence or the approximate transistor circuit of lamped element.In certain embodiments, transistor is field-effect transistor or bipolar transistor.In other embodiments, transistor is CMOS or BiCMOS.

In certain embodiments, at least one circuit element can be diode or tunnel junction.The physical medium of circuit element can be coaxial cable, waveguide, and electric wire lead-in wire, surface mount, and monolithic is one of integrated.In certain embodiments, at least one circuit element is superconductor.

Other embodiments of the invention relate to the assembly that comprises reflectionless filter of the present invention.In some embodiment of assembly, filter and other reflectionless filter, amplifier, frequency mixer, detector and/or conventional filter cascade.Assembly can be gain module, tunable optic filter, filter bank, multiplexer, signal source, up converter or down converter, reflector, receiver or transceiver.

Other embodiments of the invention relate to the method for designing of reflectionless filter.Step of the present invention comprises: be symmetrical by circuit limitations; Select a normalized impedance; Make it substantially equal the standardization input admittance of odd mode equivalent electric circuit with the standardization input impedance of restriction even-mode equivalent electric circuit.

The method can also comprise: even-mode equivalent electric circuit topological structure is restricted to one of them of bank of filters that comprises the logical and band resistance of high pass, low pass, band, one of them port stops; Odd mode equivalent electric circuit topological structure is restricted to the dual structure of even-mode circuit topological structure; Adjust the circuit topological structure of even number and odd mode, to meet symmetric condition, the behavior of holding circuit simultaneously; With the value of limiting circuit element, to also meet symmetry and antithesis condition.

Some embodiment also can be included in and on circuit node and line of symmetry, between node, add new element; Give circuit element apportioning cost to form at least one transmission pole in desired location; By multiple reflectionless filter cascades; And/or pole location is set to overlap and one of disperse.

Some embodiment can also comprise that selection approaches the physical assemblies of the circuit element circuit characteristic in reflectionless filter topological structure very much.Physical assemblies can be lamped element, transmission line and transistorized one of them.In addition, physical assemblies can be coaxial cable, waveguide, electric wire lead-in wire, surface mount and single chip integrated one of them.

In following part specification, propose other embodiments of the invention and advantage, and part is apparent or can draw from the practice of the present invention from this specification.

Brief description of the drawings

The only mode by example and be described in greater detail with reference to the attached drawings the present invention, wherein:

Fig. 1 is the block diagram of a symmetrical two-port network.

Fig. 2 is the schematic diagram of a pair of pair of high pass circuit using in the derivation of areflexia low pass filter.

Fig. 3 is after remodeling to meet the schematic diagram of a pair of pair of high pass circuit after symmetric condition.

Fig. 4 is the schematic diagram of an arbitrary order areflexia low pass filter.

Fig. 5 is the schematic diagram that expands the low pass reflectionless filter topological structure on n rank.

Fig. 6 is the figure that the analogue transmission characteristic that is suitable for single order, second order and three rank areflexia low pass filters is shown.

Fig. 7 is that to be illustrated in limit be wherein to overlap or the simulation comparison diagram of the four assistant wardens connection areflexia low pass filters that disperse.

Fig. 8 illustrates to be suitable for the analog gain (solid line) of four joint areflexia low pass filters and the figure of group delay (dotted line), and wherein inductance Q is changed to 64 from 4.

Fig. 9 a is the schematic diagram of single order low pass reflectionless filter.

Fig. 9 b is the schematic diagram of single order high pass reflectionless filter.

Fig. 9 c is the schematic diagram of first-order bandpass reflectionless filter.

Fig. 9 d is the schematic diagram of single order band resistance reflectionless filter.

Figure 10 a-10d is the frequency response curve that the firstorder filter shown in Fig. 9 a-9d is shown.

Figure 11 a be when signal during in filter passband by the signal path of circuit.

Figure 11 b be when signal during in filter stop bend by the signal path of circuit.

Figure 12 is the four assistant warden connection insertion loss of reflectionless filter and the figure of complicated gain slope that are suitable for that compare with Chebyshev filter with traditional B utterworth.

Figure 13 is the layout of areflexia low pass filter prototype.

Figure 14 is the layout of areflexia band pass filter prototype.

Figure 15 is the measurement performance of the areflexia low pass filter prototype figure to simulated performance.

Figure 16 is the measurement performance of the areflexia band pass filter prototype figure to simulated performance.

Figure 17 is the figure that has utilized the down converter of the advantage of integrated reflectionless filter.

Specific embodiment

As in this imbody and broad overview, explanation herein provides specific embodiments of the invention.But the embodiment of disclosure can be only exemplary embodiment of the present invention, and the present invention can various forms and the embodiment of replacement form.Therefore, concrete structure and function detail not intention are restrictive, and its purpose is that they provide the basis of rights and interests and implement in every way representative basis of the present invention as instruction those skilled in the art.

The problem that can be solved by the embodiment of the present invention is circuit topological structure and the designing technique that is suitable for mating good electronic filter under all frequencies.Find surprisingly, this filter has some beyond thought advantages, comprises no matter being the minimal reflection on the input and output port at them in its passband or stopband or transition band.The return loss of these filters is unlimited substantially under all frequencies.On the other hand, in traditional filter, stopband suppresses not need part instead of absorb them to realize by be reflected back frequency spectrum to signal source.Instantaneous filter is to be made up of lamped element resistance, inductor and capacitor or equivalent transmission line, and any form (as integrated in waveguide, coaxial cable, electric wire lead-in wire, surface mount, monolithic) that can be applicable to application is implemented.

Fig. 1 shows symmetrical two-port network arbitrarily.Although reflectionless filter is without symmetry, preferred embodiment is symmetrical.In such network, if these two ports encourage by the phase place of identical signal amplitude and coupling simultaneously, the electric current that traverses to another side will do not there is not so from a side of the plane of symmetry.So-called even-mode that Here it is.Equally, if two ports by identical amplitude but the phase places of 180 degree out-phase encourage, all nodes that are positioned at so on the plane of symmetry should have the zero potential with respect to ground.So-called odd mode that Here it is.

Therefore, it may have two one port networks, and each half that comprises original two-port network element, is positioned at the node open circuit on the plane of symmetry or is short-circuited to ground.These can be called even-mode equivalent electric circuit and odd mode equivalent electric circuit.Equivalent electric circuit is the circuit that retains the electrical characteristics of all former (often more complicated) circuit.Then the scattering parameter of former two-port network is given to the stack of the reflection coefficient of even-mode and odd mode equivalent electric circuit, as follows:

$s_{11}=s_{22}=\frac{1}{2}({\mathrm{\Γ}}_{\mathrm{even}}+{\mathrm{\Γ}}_{\mathrm{odd}})---\left(1\right)$

$s_{21}=s_{12}=\frac{1}{2}({\mathrm{\Γ}}_{\mathrm{even}}-{\mathrm{\Γ}}_{\mathrm{odd}})---\left(2\right)$

Wherein s _ijthe scattering coefficient from port j to port i, and Γ _evenand Γ _oddit is respectively the reflection coefficient of even-mode and odd mode equivalent electric circuit.Therefore, the condition that is suitable for perfect Input matching S11=0 comes from (1), as follows:

Γ _even＝-Γ _odd (3)

This as much as to say even-mode input impedance be (or vice versa) equating with standardized odd mode input admittance:

z _even＝y _odd (4)

Wherein z _evenstandardized even-mode impedance, and y _oddbe standardized odd mode admittance, if even-mode and odd mode circuit are mutual antithesis (as inductor is replaced by capacitor, vent diverter is replaced by series element), this is satisfied.In addition,, in conjunction with (2) and (3), the transfer function of two-port network originally is directly provided by even-mode reflection coefficient:

s ₂₁＝Γ _even (5)

In practice, on mathematics, perfectly Input matching cannot obtain ideally.In addition, in some applications, a small amount of degradation that allows wittingly the Input matching that is conducive to other filter characteristic (as cut-off steepness) can be favourable.In this case, equation (3), (4), (5) will only retain approximate authenticity.

Utilize equation (4) and (5) can obtain being suitable for the topological structure of areflexia low pass filter, areflexia high pass filter, areflexia band pass filter and areflexia band stop filter.For convenience of description, describe the derivation of low pass filter, but similarly program can be made for obtaining areflexia high pass filter by those skilled in the art, areflexia band pass filter, and areflexia band stop filter.

Fig. 2 shows two high pass circuits.Fig. 2 left side shows a high pass filter, and its one end ends at even-mode circuit.Because the transmission characteristic of this even-mode filter is high pass, reflection characteristic can be low pass, thereby two total ports can be also low passes.This network duality is depicted as odd mode equivalent electric circuit by right side at Fig. 2.

Circuit shown in Fig. 2 may not can be revealed as even-mode and the odd mode assembly of two-port network as shown in Figure 1, does not meet symmetric condition because they are revealed as.But, can recover symmetry by the remodeling that topological structure is not affected to circuit behavior.For example, such step is shown in Figure 3.

Comprise in the step shown in Fig. 3 (be not must in this order):

A) between the input node of even-mode circuit and the plane of symmetry, increase inductor.Because the plane of symmetry is equivalent to the open circuit of even-mode, this inductor is inoperative.

B) put upside down the order of electric capacity and resistance, they are connected at the end of even-mode circuit.

C) will directly connect from step B) electric capacity and the node between resistance be dragged to the plane of symmetry.This becomes open circuit in even-mode, and on circuit behavior without any impact.

D) change the ground connection of the first shunted resistively inductance device in odd mode circuit into virtual ground (it is limited by the plane of symmetry odd mode) from absolute ground connection.

E) change virtual ground the ground connection of the output resistance of odd mode circuit into by absolute ground connection.

F) in odd mode circuit, definitely between ground connection and virtual ground, increasing a capacitor.Due to two-terminal-grounding, on circuit behavior without any impact.

Fig. 4 shows an embodiment of the areflexia low pass filter topological structure of formation.

Symmetry shows that the inductor that is assigned to and the particular value of capacitor should equate in both sides, meet antithesis condition implicit in Fig. 2 simultaneously.In addition, can obtain additional flexibility by increase vent diverter between circuit node and the plane of symmetry, it keeps symmetry and dual numbers mode circuit not to affect, but provides the extra degree of freedom for odd mode circuit values.Equally, the element of any type can increase with the mode of final capacitor's series, then just before resistor, carries out balance by the antithesis assembly by the plane of symmetry.These operate all preserved symmetry and allow to meet antithesis restriction.

Fig. 5 shows another embodiment of areflexia low pass circuit topological structure.Can be subject to limiting to meet antithesis condition as follows in the value of circuit element as shown in the figure:

$C_1=\frac{1}{Z_0^2}\·\frac{L_{a,1}}{2}---\left(6\right)$

$L_{b,k}=Z_0^2\·C_{k-1}---\left(7\right)$

$C_k=\frac{1}{Z_0^2}\·\frac{L_{a,k}{L}_{b,k}}{L_{a,k}+2L_{b,k}}---\left(8\right)$

$C_{n+1}=\frac{1}{Z_0^2}\·\frac{2L_{a,n+1}{L}_{b,n+1}}{L_{a,n+1}+2L_{b,n+1}}---\left(9\right)$

$L_x=Z_0^2{C}_x---\left(10\right)$

$R_2=Z_0^2\·\frac{{2R}_1}{R_1^2-Z_0^2+{2R}_1{R}_3}---\left(11\right)$

In above-mentioned equation, Z ₀it is normalized impedance.Additional element may not can cause better filter response, thereby usually can omit completely, like this:

R ₂＝∞ (12)

R ₃＝0 (13)

L _a，k＝∞ k＞1 (14)

L _x＝C _x＝0 (15)

Fig. 6 shows single order, the analog response of second order and three rank areflexia low pass filters.Although higher order filter may cause pulse shaper cut-off characteristics, they also may form the outer peak value of higher band.Stopband peak value for firstorder filter, be just-14 decibels once, for second order filter, be below-4 decibels, and for three rank filters, be below-2 decibels.Therefore, preferred embodiment adopts firstorder filter.

Improved filter characteristic can be saved and be realized by cascading filter.Because filter section is mated substantially, therefore in their process of cascade, there is no intrinsic difficulty.In a preferred embodiment, wherein joint is single order, and every assistant warden connection suppresses the stopband that provides extra 14.5 decibels.Be different from traditional filter, reflectionless filter joint does not need work located adjacent one another.Therefore, they can be distributed in whole signal path, to meet application required dynamic range and insulation request.In addition, this filter can be cascaded to a rare amplifier, frequency mixer, detector, and traditional filter.

In the embodiment of multiple first order pole assistant wardens connection, all limits be all overlap or can be dispersion.Fig. 7 shows the comparison of these two kinds of methods.Owing to surmounting the slope relatively flat of stopband transmission characteristic of the first limit of single-pole filter, in launching, limit there is no too large advantage.Joining peak value stopbands with four assistant wardens suppresses to be only improved to 61 decibels from 58 decibels.In this level, compared with independent joint tuning, final inhibition will be depended on component tolerances.

The practical filter loss of passband will be subject to the control of inductor quality factor (" Q ") conventionally.Fig. 8 illustrate inductor quality factor q be 4,8,16,32 and 64 four joint low pass filters simulation loss, wherein Q assesses under 100MHz.Note, until utilize this circuit topological structure that Q is dropped to lower than approximately before 8, Q does not almost affect for stopband level, and can not affect passband response.In Fig. 8, also show group delay, in whole passband, there is the monotonic nature that is very similar to very big dull and stereotyped filter.

In another embodiment, after should noting in equation (12) to (15) is updated to equation (6)-(11), first inductance (L in the low pass filter topological structure of Fig. 4 _{a, 1}) and last electric capacity (C _n+1) with all the other only differ factor 2.By the first inductor being divided into two series reactors, and last capacitor is divided into two capacitors in parallel, the topological structure of result shaping filter, wherein all inductance, all electric capacity and all resistance all equate, have reduced the design problem of selecting pole frequency.Can be to high pass, band logical and band stop filter take similar saying, it can be similar to above-mentioned mode and produce.At cascade reflectionless filter joint final shown in Fig. 9 a-9d.In their corresponding frequency responses shown in Figure 10 a-10d.

The design formula that is suitable for low pass and high pass filter is:

$L=\frac{Z_0}{{\mathrm{\ω}}_p}---\left(16\right)$

$C=\frac{Y_0}{{\mathrm{\ω}}_p}---\left(17\right)$

R＝Z ₀ (18)

Wherein L is the inductance of all inductors, and C is the electric capacity of all capacitors, and R is the resistance of all resistance, ω _pthe pole frequency of radian per second, Y ₀for normalized admittance, and Z ₀for normalized impedance.Logical and the band stop filter for band, each have two limits (lower limit and upper limit), and design formula is:

$L_s=\frac{Z_0}{{\mathrm{\ω}}_s}---\left(19\right)$

$L_x=\frac{Z_0}{{\mathrm{\ω}}_x}---\left(20\right)$

$C_s=\frac{Y_0}{{\mathrm{\ω}}_s}---\left(21\right)$

$C_x=\frac{Y_0}{{\mathrm{\ω}}_x}---\left(22\right)$

R＝Z ₀ (23)

Wherein the inductance of inductor is L _xand L _sone of, the electric capacity of capacitor is C _xand C _sone of, the resistance of resistor is R, Y ₀for normalized admittance, Z ₀for normalized impedance, and

ω _s＝ω _p，2-ω _p，1 (24)

${\mathrm{\ω}}_x=\frac{{\mathrm{\ω}}_{p,1}{\mathrm{\ω}}_{p,2}}{{\mathrm{\ω}}_{p,2}-{\mathrm{\ω}}_{p,1}}---\left(25\right)$

Wherein ω _{p, 1}and ω _{p, 2}respectively upper limit and and lower pole frequency.

Although utilize resistance, electric capacity and inductance show embodiment, can use any element that can't harm or damage.Generally, filter can only comprise " damaging element " (a possible example is resistance) and " harmless element " (it can be inductor, capacitor, resonator, variable capacitance diode and/or transmission line).Some element of this outer filter can be tuned element, diode and/or tunnel junction.Although illustrated embodiment comprises the element on specific rank, these elements can be arbitrary order.In addition, in certain embodiments, two or more identical elements or two or more different elements can be together connected in series or in parallel.In filter, can use lamped element, equivalence or the approximate transmission line of lamped element, and/or equivalence or the approximate transistor circuit of lamped element, or its combination in any.If use transistor, transistor can be field-effect transistor, bipolar transistor, CMOS transistor and/or BiCMOS transistor.

Can be any medium as known in the art for the preparation of the medium of said elements, include but not limited to: coaxial cable, waveguide, electric wire lead-in wire, surface mount, and monolithic is integrated.Each circuit element can be superconductor.

Filter can be used for gain module, tunable optic filter, and filter bank, multiplexer, up converter or down converter, reflector, receiver, transceiver, or in signal source.

The path of passing through Fig. 9 a-9d median filter of taking at signal shown in Figure 11 a-11b.In this accompanying drawing, element (resistance, inductance, electric capacity, and series connection and shunting combination) is represented arbitrarily by rectangle impedance component.Filled Rectangle represents relatively low impedance, and grey color component represents relatively high impedance.When in the passband of a signal in filter, as shown in Figure 11 a, it directly from a port by arriving other port.When in the stopband of a signal in filter, as shown in Figure 11 b, its stops passes through between port, and the substitute is the absorption resistance directly sending in circuit.

The topological structure of reflectionless filter, except its areflexia performance, also has some other advantage that is better than conventional filter.In Figure 12, at 4 assistant warden connection areflexia low pass filters, there are 7 limit Chebyshev filters of 0.05dB ripple, and compare between 7 limit Butterworth filters.As shown in figure 12, complicated gain slope is starkly lower than the complicated gain slope of same frequency range Butterworth or Chebyshev filter, and this will cause having at needs more high stability and the precision of the system alignment of two filters of the complexity gain of coupling.In addition find, reflectionless filter needs than Butterworth or the lower wattless component of Chebyshev filter value, so that implement under higher frequency under identical frequency range.In addition, reflectionless filter is more tolerant for damaging assembly, and the insertion loss having is insertion loss only about half of with the Chebyshev filter of the inductor of identical Q.

Example explanation inventive embodiment below, but should not be regarded as limiting the scope of the invention.

Example

In order to test some representative embodiment, use cheapness, discrete, element pasted on surface builds and measures two prototype filters.First prototype is a low pass filter, and its four cascade first order pole joints by the filter shown in Fig. 9 a form, and wherein all four limits are tuned to 325 megahertzes.Second prototype is a band pass filter, and it is made up of three firstorder filters shown in Fig. 9 c, and upper limit and lower limit are respectively at 110 megahertzes and 310 megahertzes.In the layout of these prototypes shown in Figure 13 and 14.At their measurement and the performance curve of simulation shown in Figure 15 and Figure 16.

Compatibility between data display measurement and theory, although only used desirable resistor, inductor and capacitor in its tangible simulation.Above-mentioned illustrating in order to carry out these filters, does not need the very assembly of high-quality, especially inductor.The Q that inductor clearly has be 8 and tolerance be ± 2%, and the clear and definite tolerance of capacitor is ± 5%.Due in certain embodiments, all inductors in low pass filter have identical value, and be one of two values of band pass filter, assembly all can drag from same location in order, so mutually comparatively speaking, the relative tolerance of assembly may be better than the absolute tolerance being provided by manufacture process.For electric capacity and resistance, this also sets up.

In simulation process, reflection coefficient is zero, but in practice, and it depends on the tolerance of assembly.However, in the passband of two filters and transition band, measured return loss exceedes 65 decibels, and exceedes 35 decibels in the whole measuring range up to 1GHz.Equally, low pass filter has obtained the peak value stopband of 53 decibels to be suppressed, and 58 decibels simulate, and band pass filter obtains the level of 43 decibels, almost mates with simulating completely.Under approximately 800 megahertzes, in band pass filter, there is parasitic resonance, but because this peak value is the level of-45 decibels, unlikely cause in actual use any problem.

In another example, areflexia low pass filter is integrated in the down converter of L-band (1200-1700 megahertz), as shown in figure 17.In this embodiment, two areflexia low pass filters are used as to frequency overlapped-resistable filter.Each filter is made up of 4 joints of Fig. 9 a shown type.They with such as other assembly cascade of amplifier and frequency mixer, and be distributed in whole IF path, to make all component utilize best that band is outer fills, and the dynamic range in receiver is maximized.This filter adopts cheap element pasted on surface to carry out.Complexity between filter gain coupling (when compared with other filter type as shown in figure 12) allows this down converter to obtain the mirror image higher than 50 decibels measured under the ambient temperature ranges that exceeding 12 degree Celsius to suppress.

After having considered specification of the present invention disclosed herein and practice, other embodiment of the present invention and use are apparent for those skilled in the art.The all references of herein enumerating, comprises all publications, and the U.S. and foreign patent and patent application, all clearly and be all hereby expressly incorporated by reference.Specification and example intention are regarded as merely exemplary, because true scope of the present invention and spirit are limited by following claim.In addition, term " comprise " comprise term " by ... form " and " substantially by ... formation ".

Claims (40)

1. areflexia electronic filter, comprising:

Symmetrical two-port circuit, wherein, when two ports are during respectively with homophase and 180 ° of driven out-of-phase, forms symmetry by even-mode and odd mode equivalent electric circuit;

Wherein at least one circuit element in symmetrical two-port circuit comprises that at least one harmless element and at least one damage element, and described at least one harmless element and at least one damage element and be arranged so that:

The standardization input impedance of even-mode equivalent electric circuit equals the standardization input admittance of odd mode equivalent electric circuit substantially; And

The standardization input impedance of odd mode equivalent electric circuit is substantially equal to the standardization input admittance of even-mode equivalent electric circuit.

2. areflexia electronic filter according to claim 1, wherein at least one harmless element is selected from the group being made up of following: inductor, capacitor, resonator, transmission line, variable capacitance diode and combination thereof, wherein at least one damages element and is selected from the group being made up of following: resistor, rheostat and combination thereof.

3. areflexia electronic filter according to claim 2, wherein exists and has some inductors of identical inductances and have some capacitors of same capacitance.

4., wherein there are some resistors with same resistance in areflexia electronic filter according to claim 2.

5. areflexia electronic filter according to claim 2, wherein areflexia electronic filter is band pass filter or band stop filter, wherein exists and has some inductors of one of the first inductance and second inductance and have the first electric capacity and some capacitors of one of the second electric capacity.

6. areflexia electronic filter according to claim 2, wherein areflexia electronic filter is low pass filter or high pass filter, and

$L=\frac{Z_0}{{\mathrm{\ω}}_p}$

$C=\frac{Y_0}{{\mathrm{\ω}}_p}$

R=Z ₀

Wherein L is the inductance of all inductors, and C is the electric capacity of all capacitors, and R is the resistance of all resistance, ω _pthe pole frequency of radian per second, Y ₀for normalized admittance, and Z ₀it is normalized impedance.

7. areflexia electronic filter according to claim 2, wherein areflexia electronic filter is band pass filter or the band stop filter with the first limit and the second limit, and

$L_s=\frac{Z_0}{{\mathrm{\ω}}_s}$

$L_x=\frac{Z_0}{{\mathrm{\ω}}_x}$

$C_s=\frac{Y_0}{{\mathrm{\ω}}_s}$

$C_x=\frac{Y_0}{{\mathrm{\ω}}_x}$

R=Z ₀

Wherein the inductance of inductor is L _xand L _sone of, the electric capacity of capacitor is C _xand C _sone of, the resistance of resistor is R, Y ₀for normalized admittance, Z ₀normalized impedance, and

ω _s＝ω _p，2-ω _p，1

${\mathrm{\ω}}_x=\frac{{\mathrm{\ω}}_{p,1}{\mathrm{\ω}}_{p,2}}{{\mathrm{\ω}}_{p,2}-{\mathrm{\ω}}_{p,1}}$

Wherein ω _{p, 1}and ω _{p, 2}respectively the first and second pole frequencies.

8. areflexia electronic filter according to claim 1, wherein at least one circuit element is tunable.

9. areflexia electronic filter according to claim 1, wherein areflexia electronic filter is selected from and comprises following bank of filters: low pass filter, high pass filter, band pass filter and band stop filter.

10. areflexia electronic filter according to claim 1, wherein areflexia electronic filter is selected from and comprises following bank of filters: two band filter and multi-band filter.

11. areflexia electronic filters according to claim 1, also comprise:

At least one node in each side of symmetrical two-port circuit; And

At least one element between node in each side of symmetrical two-port circuit.

12. areflexia electronic filters according to claim 1, also comprise the additional circuit element of the duality of holding circuit symmetry and even-mode and odd mode equivalent electric circuit.

13. areflexia electronic filters according to claim 1, wherein areflexia electronic filter is selected from the group being made up of following: firstorder filter, second order filter and higher order filter.

14. areflexia electronic filters according to claim 1, wherein each side of the both sides of symmetrical two-port circuit comprises:

Port node;

The first internal node;

The second internal node;

Port node is connected to the harmless element of the first type of node on line of symmetry;

Port node is connected to the harmless element of the second type of the first internal node;

By the harmless element of the first type of the first internal node ground connection;

The first internal node is connected to the element that damages of the second internal node;

By the harmless element of the second type of the second internal node ground connection; And

Direct connection on the second internal node and line of symmetry between node.

15. areflexia electronic filters according to claim 14, wherein damaging element is resistor.

16. areflexia electronic filters according to claim 14, wherein the harmless element of the first type is inductor, and wherein the harmless element of the second type is capacitor.

17. areflexia electronic filters according to claim 14, wherein the harmless element of the first type is capacitor, and wherein the harmless element of the second type is inductor.

18. areflexia electronic filters according to claim 14, wherein the harmless element of the first type is inductor and capacitor in parallel, and wherein the harmless element of the second type is inductor and the capacitor of series connection.

19. areflexia electronic filters according to claim 14, wherein the harmless element of the first type is inductor and the capacitor of series connection, and wherein the harmless element of the second type is inductor and capacitor in parallel.

20. areflexia electronic filters according to claim 1, wherein some areflexia electronic filters cascade.

21. areflexia electronic filters according to claim 20, the areflexia electronic filter of its cascade comprises limit, limit is overlap or one of disperse.

22. areflexia electronic filters according to claim 1, wherein areflexia electronic filter scalable or conversion.

23. areflexia electronic filters according to claim 1, wherein circuit element is selected from the group being made up of following: the equivalent transistor circuit of the equivalent transmission line of lamped element and lamped element.

24. areflexia electronic filters according to claim 23, wherein transistor is that field-effect transistor, bipolar transistor, CMOS transistor or BiCMOS are transistorized one of at least.

25. areflexia electronic filters according to claim 1, wherein at least one circuit element is selected from the group being made up of following: diode and tunnel junction.

26. areflexia electronic filters according to claim 1, wherein the physical medium of circuit element is one of coaxial cable, waveguide, electric wire lead-in wire and surface mount.

27. areflexia electronic filters according to claim 1, wherein at least one circuit element is selected from the group being made up of following: the integrated and superconductor of monolithic.

28. areflexia electronic filters according to claim 1, wherein one of at least cascade of areflexia electronic filter and additional areflexia electronic filter, amplifier, frequency mixer, detector and/or conventional filter.

29. areflexia electronic filters according to claim 1, wherein areflexia electronic filter can be used for gain module, tunable optic filter, filter bank, multiplexer, up converter, down converter, reflector, receiver, transceiver and signal source one of at least in.

The method of 30. design areflexia electronic filters, comprises the steps:

Symmetrical two-port circuit is provided, wherein, when two ports are during respectively with homophase and 180 ° of driven out-of-phase, forms symmetry by even-mode equivalent electric circuit and odd mode equivalent electric circuit;

Limit the two-port circuit of described symmetry, thereby make the standardization input impedance of even-mode equivalent electric circuit be substantially equal to the standardization input admittance of odd mode equivalent electric circuit; And the standardization input impedance of odd mode equivalent electric circuit is substantially equal to the standardization input admittance of even-mode equivalent electric circuit.

31. methods according to claim 30, also comprise:

Even-mode equivalent electric circuit topological structure is restricted to comprise that high pass, low pass, band lead to, bank of filters with resistance, biobelt and multi-band one of them, one of them port stops;

Odd mode equivalent electric circuit topological structure is restricted to the dual structure of even-mode equivalent electric circuit topological structure;

Adjust even-mode equivalent electric circuit and odd mode equivalent electric circuit topological structure, to meet symmetric condition, the characteristic of holding circuit simultaneously; And

The value of Circuit tuning element, to meet symmetry and antithesis condition.

32. methods according to claim 31, wherein adjust even-mode equivalent electric circuit and odd mode equivalent electric circuit topological structure comprise following one of at least:

In even-mode equivalent electric circuit, between circuit node and line of symmetry, add element;

By the ground connection of the circuit element in odd mode equivalent electric circuit at definitely one of ground connection and virtual ground with definitely change between another of ground connection and virtual ground;

Change the exponent number of series element;

Circuit node in even-mode equivalent electric circuit is connected to line of symmetry; And

In odd mode equivalent electric circuit, definitely between ground connection and virtual ground, increasing an element.

33. methods according to claim 30, are also included in and between the node on circuit node and line of symmetry, increase a new element.

34. methods according to claim 30, also comprise increase add ons, so that the duality of holding circuit symmetry and even-mode and odd mode equivalent electric circuit.

35. methods according to claim 30, also comprise that one of at least apportioning cost to circuit element is to form at least one transmission pole in desired location.

36. methods according to claim 30, also comprise the cascade of multiple areflexia electronic filter.

37. methods according to claim 36, also comprise that the pole location of the areflexia electronic filter of cascade is set to overlap and one of disperse.

38. methods according to claim 30, also comprise that selection approaches the physical assemblies of the circuit characteristic of at least one circuit element in areflexia electronic filter topological structure very much.

39. according to the method described in claim 38, wherein physical assemblies be lamped element, transmission line, transistor, coaxial cable, waveguide, electric wire lead-in wire and surface mount one of them.

40. according to the method described in claim 38, and wherein at least one physical assemblies is selected from the group being made up of following: the integrated and superconductor of monolithic.